Screen printing apparatus



INVENTORS DOUGLAS H ARDY JR REDERICKJ 8 Sheets-Sheet 1 C. D. HARDY, JR., ETAL SCREEN PRINTING APPARATUS Dec. 7, 1965 Filed Oct. 24, 1961 CHARLES V ERONIMUS 7 M W ATTOF; s

t 3 mm mm 1965 c. D. HARDY, JR.. ETAL 3,221,646

SCREEN PRINTING APPARATUS Filed 001:. 24, 1961 8 Sheets-Sheet 2 Flg. 20

CYL. POWER SOURCEQ CONTROL IT/H36 T HYD- V LVE I03 INVENT CHARLES DOUGLAS 32am JR BYFREDE ICK JERON MUS TTORNE c. D. HARDY, JR., ETAL 3,221,646

Dec. 7, 1965 SCREEN PRINTING APPARATUS 8 Sheets-Sheet 5 Filed Oct. 24, 1961 DYJR- MUS INVENTORS DOUGLAS H AR FREDERICK JERGH TORNEY CHAR LES Dec. 7, 1965 Filed Oct. 24, 1961 Fig.5

c. D. HARDY, JR., ETAL 3,221,646

SCREEN PRINTING APPARATUS 8 Sheets-Sheet 4 INVENTORS CHARLES DOUGLAS H A R DY JR BYFRED RICK JERONIMUS ATTORNg Dec. 7, 1965 c. D. HARDY, JR., ETAL 3,221,646

SCREEN PRINTING APPARATUS 8 Sheets-Sheet 6 H a mmfl A Y MO S 0 AR m m "w. M 0 LI L T r NGR T I U A O 0 O S Y m E 7 L R A H C Filed Oct. 24, 1961 Dec. 7, 1965 C. D. HARDY, JR., ETAL SCREEN PRINTING APPARATUS Filed Oct. 24, 1961 8 Sheets-Sheet 7 Dec. 7, 1965 C. D. HARDY, JR., ETAL SCREEN PRINTING APPARATUS 8 Sheets-Sheet 8 Filed 001:. 24, @961 INVENTOF$ CHARLES DOUGLAS HARDY JR- BYFREDE ICK JERONI us /2TTORNEY United States Patent 3,221,646 SCREEN PRINTING APPARATUS Charles D. Hardy, Jr., Green Village, and Frederick Jercnimus, Lincoln Park, N .J assignors to Fritz Buser AG, Maschinenfabrik, Ozendorf, Switzerland, a corporation of Switzerland Filed Oct. 24, 1961, Ser. No. 147,294 5 Claims. (Cl. 101-115) This invention relates to screen printing techniques and more particularly to those for effecting continuous printing of multi-color successive repeated patterns on sheet material such as paper or plastic whose surface does not readily absorb ink or coloring material, and also relates to novel techniques and means for avoiding smears or blurs at the junctions between adjacent printed repeats.

In current screen printing machines used for printing colored patterns having regular repeats on textile material, it conventional to use a series of silk screens which are lowered successively into contact with the sheet of textile material and through which the coloring material is pressed, as by a squeegee arrangement, onto the sheet material. That portion of each screen which is not to print the particular color it bears is blocked out so that the coloring material does not pass through the blockedout portions during squeegee operation.

The screens which are generally employed for applying different colors of the repeat are of substantially larger dimensions than the portion of the repeat each is intended to print. When such a screen is lowered for the first time onto the material for printing of a first repeat, no difliculty is encountered. The screen then, however, is lifted and the textile material is advanced the distance of a full repeat. The screen is then again lowered onto the sheet to print the adjacent repeat pattern. At this time, because the screen is broader and wider than the repeat pattern itself, its leading edge overlies the trailing edge of the initial repeat pattern that has been imprinted. Since with textile material, the coloring material printed on the first repeat has already been absorbed into the surface of the textile material, this overlap usually causes no difiiculty in smearing or blurring the trailing edge of the first repeat print.

However, unsightly smears and blurs occur when the sheet material, on which the repeat prints are printed, does not absorb the coloring material. The problem arises because the screen must inevitably be longer and wider than the repeat pattern itself. Thus, when the screens are lowered to print the second repeat print, the screens leading border comes in contact with the trailing portion of the first repeat print and because the first repeat print has not dried the overlap portion becomes smeared. Accordingly, it becomes impractical to print in the above fashion on plastic, non-absorbent paper or other non-absorbent materials.

It is necessary to provide an eifective technique for drying the deposited color of each printed repeat between successive printings of each screen so as to avoid smearing or blurring. In conventional machines, the advance of the sheet material a single distance of a repeat pattern after a first repeat has been printed thereon, projects the leading portions of the first printed repeat into a region where it could be dried. However, the trailing portion of the repeat pattern that has been printed is not advanced sufficiently intothe drying zone to insure complete drying of such trailing portion before the screen again moves down for printing of the second adjacent repeat pattern. In consequence, the overlap of the screen on the still wet trailing portion of the first printed repeat smears the overlapping area.

Of course the screens could be maintained in elevated unprinting position for long-enough periods to insure full drying of each printed repeat pattern. Unfortunately, that would so slow down operation of the machine as to make it uneconomical to operate.

Objects and features of the present invention are to provide a novel technique that will insure effective drying of the trailing ends of each printed repeat before the commencement of printing of the next adjacent repeat without materially decreasing the speed of operation of the machine and thereby providing an economical arrangement and method for avoiding smears or blurs from occurring at the overlapping area.

In carrying out the technique of the instant invention, an arrangement is provided whereby a screen intended to print a repeat pattern is lowered to print on the material. The screen is then lifted and the sheet material advanced a distance equal to the repeat distance of the pattern plus an over-advance distance into or beneath a dryer. The dryer rapidly dries the entire repeat pattern. Immediately thereafter, the sheet material is retracted the distance of the overadvance and the screens are lowered to print the second repeat print next to the dried first repeat print.

In general, it is desirable that the retractive movement of the sheet material exactly equal the overadvance so .that there will be neither discontinuities in the pattern nor darker printed areas where the repeat prints might overlap and print twice. In particular, where multiple color printing is involved, it is essential that the retractive movement exactly equal the overadvance so that the second color will properly register with the first color.

Accordingly, another object of this invention is to pro vide means for effecting forward motion of the sheet material after each printing of a distance equal to the repeat distance plus an overadvance and then a retractive movement exactly equal to the overadvance distance to obtain registry of adjacent repeat prints and of multiple colors.

In an existing textile screen printing machine, the ad- Vance of the sheet material to be printed is effected by advancing a movable table, maintained under vacuum, the distance of a repeat pattern. During such forward advance, the vacuum maintained on the movable table holds the sheet material to the table surface and moves it forward a corresponding distance. This distance ordinarily is adjusted to the desired repeat distance. Once such forward movement has been completed, the vacuum is released and the table is retracted without, however, retracting the advanced sheet material because of the vacuum off condition. After the table has retracted, vacuum is applied to adjacent stationary portions of the table to provide a firm grip on the sheet material and while this condition is maintained, printing is effected. Upon completion of printing, vacuum in the stationary parts of the table is cut off and the next repeat advance with vacuum on in the movable table is made. This repetitive cycle provides for printing of successive repeat patterns and is effective if the material being printed is textile material which absorbs the ink or other color print quickly.

It is necessary to modify this machine and the movements imparted to the sheet material if the latter is plastic or has a non-absorbing surface. The arrangement provided by the invention is to alter the movements of the sheet material between printings. Thus, after the printing of the first repeat pattern has been effected with vacuum on the stationary portions of the table the vacuum is switched off the stationary portions of the table, and applied to the movable table. With vacuum on the movable portion, the sheet material is advanced forward a distance equal to that of the repeat pattern plus a selected over-advance distance. In one embodiment, eight inches was found to be a useful over-advance distance. Upon completion of this forward movement, the entire first repeat pattern that has been printed has been carried to a position under a drying hood to which hot drying air is blown to quick dry the entire printed repeat. During this drying operation, vacuum is released from the movable table portion which starts to retract toward its starting position. While retracting, it reaches a position such that its remaining travel to its initial position equals the over-advanced distance. Vacuum is then restored to the moving table so that it again grips the sheet material and in moving backward the final distance, which is equal to the initial over-advanced distance, carries back the dry sheet material exactly the amount of the initial overadvance. Immediataely when this position of registry of the retracted sheet material is achieved, the retractive movement of the movable table stops and vacuum is switched to the fixed portions of the table to hold the sheet material. The first screen is then lowered and the imprint of the second repeat pattern is applied contiguous to the registering trailing edge of the first dry printed repeat.

The successive screens along the length of the machine which print differently colored portions of each repeat pattern are positioned at the appropriate points along the length of the machine so that exactly the same type of color printing with a different color in successive contiguous repeats occurs at each of the succeeding screens.

Other objects and features of the invention will become apparent from the following specification and the accompanying drawings forming a part thereof, wherein:

FIG. 1 is a diagrammatic showing of the successive movements of the sheet material being printed during printing and drying by a screen printing machine in accordance with the techniques of this invention. The stages A, B, C and D of said figure represent successive positional movements of each repeat pattern in the required sequence of the novel technique practiced herein;

FIG. 2A is a schematic longitudinal cross section of the device of this invention.

FIG. 2 is a fragmentary portion of FIG. ZA showing the movable table during the advancement of the sheet material.

FIG. 3 is a cross section taken along the line 3-3 in FIG. 2.

FIG. 4 is a fragmentary longitudinal cross section showing the movable table during the retraction of the sheet material.

FIG. 5 is a fragmentary longitudinal cross section showing the movable table during the printing of the repeat print.

FIG. 6 is a schematic and block diagram of the electrical, hydraulic and vacuum systems incorporated in the embodiment illustrating the invention.

FIG. 7 is in three parts, FIG. 7A, FIG. 7B and FIG. 7C, and is the full schematic development of the block diagram of FIG. 6.

With reference first to FIG. 1, the method can best be illustrated by showing four stages in the printing of a multi-color print. At stage A, the screens 34 are lowered to print the blue portion of repeat print 4 and the yellow portion of repeat print 1. At stage B the material has been advanced a distance equal to the length of the repeat print plus an overadvance distance x so that the just printed repeat prints 4 and 1 are entirely under the drying hoods 37. At this stage B, the screens 34 are raised and no printing takes place. At stage C, the material has been retracted by the amount of the overadvance x so that repeat prints 5 and 2 may be printed contiguous to the repeat prints 4 and 1 respectively. Thus the screens 34, at stage C print a blue repeat print 5 continuous with the now dried blue repeat print 4 and also print a yellow repeat print 2 continuous with the now dried repeat print 1. Since the progress of the material being printed on is from left to right in FIG. 1, the repeat prints 1 and 2 which are shown being printed yellow have had their blue portion printed at earlier stages. At stage D, the material has again been advanced a distance equal to the length of the repeat print plus an overadvance x so that the just printed repeat prints 2 and 5 are under the drying hoods 37 preparatory to the next retraction stage where repeat prints 3 and 6 will next be printed continuous with repeat prints 2 and 5.

FIG. 2A gives a broad picture of the machine showing the materials to be printed as being fed from left to right. The material to be printed is a sheet material which is fed into the printing area of the machine from a roll R and through a standard input tensioning device 27. After passing through the printing zones, where in the printing screens 34 and drying hoods 37 operate as will be described below, the material S passes through a final dryer 28 and through a standard tensioning device 29 to be wound up as printed material on a wind-up roll WR. The table 11 over which the material S passes is connected to the hydraulic and vacuum systems in a manner that is best described in connection with the other figures.

As may be seen in FIGS. 2, 3, and 6, the machine includes a substantially fiat elongated horizontal table 11 comprising a pair of parallel stationary side sections 12 and 13 separated by a movable center section 14. These three sections 12, 13 and 14 of the table extend substantially the full length of the machine, and each has a multitude of perforations 16 in its upper surface communicating respectively with underlying vacuum chambers 18, 19 and 20. The side vacuum chambers 18 and 19 are connected through vacuum conduits 21 to an electrically-controlled vacuum reverser 22, which in turn is connected to a source of vacuum (not shown) by a conduit, 23 so that vacuum can be turned on and off with respect to the stationary side sections 12 and 13 of the table 11 during the cyclic operations to be described.

The movable center section 14 is connected by a conduit 25 to the vacuum reverser 22 so that vacuum can be maintained either on the center section 14 or on the side sections 12 and 13 as required by the particular phase in the cyclic operation of the machine.

A plurality of printing screens 34 of conventional kind are provided each intended to apply a different color pattern part to the sheet material. These screens 34 are of the kind commonly used in screen printing machines and are dimensioned to span the sheet being printed as illustrated in FIG. 3. They are located at selected spaced positions along the length of the machine so that each, when operated for printing, will apply the coloring material intended in the desired pattern to the respective pattern repeats underlying the respective screens at appropriate times as above described. The screen surfaces of these screens 34 are provided with a pattern to be imprinted by each, and the deposit of coloring material or printing ink from each screen on to the sheet material is effected by the movement of a squeegee or doctor blade 36 across the respective screen surfaces. The screens 34 are supported above the surface of the table 11 and are alternately lowered for printing and elevated to non-printing position as required during impression of the repeat pattern onto the sheet material.

A drying hood 37 is positioned between each pair of adjacent screens 34. These hoods 37 are positioned to overlie the sheet on the table top and all are connected by feed ducts 38 and exhaust ducts 39 to a common hot air supply duct 40 and exhaust duct 41. Thus, heated air supplied to the supply duct 40 will circulate via ducts 38 through the drying hoods 37 into contact with the underlying surface of the sheet below the hoods 37 and be withdrawn via ducts 39 and the exhaust duct 41.

A vacuum system, a hydraulic system and an electrical system operate in conjunction with one another to perform and control the sequence of operations essential to the invention.

The major function of the hydraulic system is to move the center movable table 14. Ancillary to this major function is an hydraulic cushion at the end of each forward and backward movement of the center table 14. This cushion is supplied by the hydraulic system through throttling control pistons 61 and 98.

The function of the vacuum system is to supply a hold on the material to be printed. The vacuum hold will be exerted by the movable center table 14 when the material is to be moved forward or back and by the stationary side tables 12 and 13, during the printing operation.

The electrical system is a relay control system to assure the proper sequence and coordination of operations; to switch the vacuum from center to side tables at the proper time; to switch the hydraulic pressure from forward to back and vice-versa; to coordinate the backward movement of the material to compensate for the forward over-advance with the switch in vacuum from the side tables 12 and 13 to the center table 14; and to perform other such functions as will be described in greater detail below.

As is illustrated in FIGS. 2, 4, 5, and 6, the movable power cylinder 42 is permanently connected to the movable center table 14 and supplies motive power to that table 14. Fixed piston 45 in power cylinder 42 divides the cylinder 42 into two chambers 43L and 43R. Fixed hollow piston rods 46L, 46R extend axially through the movable cylinder 42 from each end of the fixed piston 45. The outer ends of the piston rods 46L, 46R are secured to fixed supports 87 and 62 respectively, which supports 87 and 62 are secured to the frame of the machine. In a preferred embodiment, these fixed supports 87, 62 are adjustable as to their spacing apart to permit adjusting the length of the stroke of the power cylinder 42 and thus permit machine flexibility as to the dimensions of the repeat print that may be used.

Holes 50 in the walls of piston rods 46L, 46R permit fluid under pressure to be pumped into or drained out of chambers 43L, 43R. The hollow interior of piston rods 46L, 46R are connected through conduits 51L, 51R and thence through the advance-return hydraulic control valve 52 to a hydraulic pump and oil tank (not shown). The control valve 52 functions to alternately direct the fluid under pressure first to one side of the piston 45 and then to the other side. As seen in FIG. 7B, the control valve 52 is in return position, so that fluid under pressure from the main pump line 55 is admitted to conduit 51L and thence through piston rod 46L into chamber 43L. The pressure build-up in chamber 43L between the fixed piston 45 and the movable cylinder 42 causes the cylinder 42 to return to its starting position, which is to move to the left as seen in FIG. 4. As the cylinder retracts to the left, the fluid in the right chamber 43R drains back to the oil tank through the hollow piston rod 46R, conduit 51R, control valve 52 and return throttling valve 56. The position of the control valve 52, that is whether it is in the return or advance position, is determined by operation of the advance-return solenoid 58 and advance-return control relay 59. The solenoid 58 and relay 59 will be discussed in greater detail in connection with the whole electrical system.

When the solenoid 58 switches the control valve 52 to the advance position, the fluid under pressure from line 55 is admitted to conduit 51R and thence through rod 46R into chamber 43R to cause to the cylinder 42 to advance to the right. As the cylinder advances, the fluid in the left chamber 43L drains out through the hollow piston rod 46L, conduit 51L, control valve 52 and advance throttling valve 60.

The following description of the machine operation will assume that the machine has been running and that the stop button 72 has been pushed during the actual printing, that is, while the screens 34 were down on the print table table and the squeeqees 36 were moving across the screens 34. When the stop button 72 is pushed during the actual printing, the machine completes that print and then stops. When the go button 73 is next pressed, the machine, in broad terms, will go through the following cycle: The screens 34 will be lifted and the squeegee 36 drive stopped. The material will then be advanced the length of the repeat pattern plus the over-advance. The material will next be dried while the movable table 14 returns to its initial position. reaches a distance short of its return position by the amount of the over-advance, the vacuum will shift to permit the table 14 to grab hold of the material and retract the material by the amount of the over-advance. Finally the actual printing operations will take place and this cycle will be repeated.

In more specific terms, the following description will treat the cycle as having eight phases through which the machine automatically cycles during operation. These eight phases are: 1) printing completed, (2) advance travel, (3) advance completed, (4) drying and return travel, (5) at over-advance contact, (6) over-advance return travel, (7) return completed, and (8) printing. This eight phase cycle is arbitrarily set as a convenient way of breaking down the description into more easily un derstandable segments. However, where it would aid understanding to tie in aspects of one phase with another, the following description will depart from a strict limitation to a phase-by-phase description.

When the go button 73 is pressed, the stop-go relay 74 is energized and by means of its first contact 74a is held energized when the go button 73 is released. The stop-go relay 74 remains energized throughout the machine operation and will become de-energized only after the stop button 72 is pressed.

Printing completed phase Before the go button 73 is pressed, the primary squeegee control relay 76 and both secondary squeegee control relays 77 and 78 are energized because that was their state at the end of the actual printing phase and the stopping of the machine does not change that state as long as all voltages are not removed. It should be pointed out that the lift-off piston 82 is at a completely lowered position, as are the screens 34 which piston 82 controls, at the end of the printing phase. Thus the lift-off down micro-switch 84 is closed and supplies voltage to primary squeegee control relay 76 through the holding circuit established by contact 76a and the relay 76 remains energized even after the stop button has been pressed.

When the stop-go relay 74 is energized by the go button 73, a path is completed through contacts 78e, 77d and 74b to energize lift-01f control relay 80. Energizing the lift-off control relay 80, switches the lift-off solenoid 81 and lines up the ports on the hydraulic lift-off valve 83 to send the lift-off piston 82 upwards from an entirely lowered position, thus lifting the screens 34 from the table. As the lift-off piston 82 proceeds up it contacts the lift-off down micro-switch 84 thereby de-energizing primary squeegee control relay 76 which in turn causes the secondary squeegee control relays 77 and 78 to be de-energized. This removes the AC. voltage on the lift-off control relay thereby de-energizing relay 80 so that the lift-ofi piston 82 remains in an intermediate position, as shown in FIG. 73, holding open micro-switch 84.

The power cylinder 42, which is connected to the movable center table. 14, is in the completely retracted position during the printing phase and thus is in that position during the printing completed phase. It is during this printing completed phase that changes take place which puts the power cylinder 42 and table 14 in condition to advance and consequently move the material forward. The lifting of the screens 34, just described, is one such preparatory-to-advance operation. Another, is to assure that the vaccum is placed on the movable center table 14 rather than the end tables 12 and 13. The power cylinder 42, being in the completely retracted position, holds closed the return contact block switch 87s which energizes As the movable table 14 the return completed relay 88 which, through contact 88c, supplies positive voltage to terminal 90a of vacuum reverser solenoid 90. Positive voltage on terminal 90a of solenoid 90 causes the vacuum to be placed on the center table 14 and left off the fixed outside tables 12 and 13.

The advance-return solenoid 58 receives positive voltage through terminal 58a, since advance-return control relay 59 is unenergized. Positive voltage on terminal 58a causes the ports in the advance-return hydraulic control valve to line up so that fluid under pressure is supplied to the right hand chamber 43R of the power cylinder 42.

Accordingly, with the screens 34 lifted, the vacuum on the center table 14, and the control valve 52 set up to supply oil under pressure to the right hand chamber 43R, the machine is prepared to advance the paper.

Advance travel phase The oil under pressure supplied to the right chamber 43R of power cylinder 42 causes the cylinder 42, the attached center table 14 and the material held onto the table 14 by vacuum, to all advance to the right as seen in FIG. 2. Return contact block switch 87 opens as soon as the cylinder 42 advances, but a holding circuit through contact 92a of advance completed relay 92 holds return completed relay 88 energized throughout the advance travel. It is necessary to hold relay 88 energized so that positive voltage will be supplied through Contact 880 to terminal 90a of the vacuum reverser solenoid 90 and the vacuum maintained on the moving center table 14 throughout the advance travel.

The advance travel is stopped by an advance contact block 62 which block is located a distance from the return contact block equal to the repeat print length plus the over-advance distance. To minimize shock and damage and noise an advance throttling control piston 61 causes a gradual deceleration at the end of the advance travel.

Advance completed phase The power cylinder closes the advance contact block swtich 62s upon contacting the block 62. The closed switch 62s energizes advance completed relay 92 which breaks contact 92a and thus de-energizes relay 88. The consequent opening of contact 880 and closing of contact 920 switches positive voltage from contact 94d to contact 940 of vacuum reverser relay 94 and thus switches the vacuum reverser solenoid 90, since positive voltage is thereby switched from terminal 90a to terminal 9%. Accordingly, the vacuum is taken off the movable center table 14 and placed on the end tables 12 and 13 for the purpose of holding the sheet in the advanced position during the next phase of the cycle when the movable center table 14 retracts.

The energization of advanced completed relay 92 closes contact 92d and thus energizes the advance-return control relay 59. An energized relay 59 switches the advancereturn solenoid 58 by switching positive voltage from terminal 58a to terminal 58b. Accordingly, the ports in the hydraulic control valve 52 realign to supply fluid under pressure to the left hand chamber 43L of the power cylinder 42. The advance-return control relay 59 has a half second lag in its operation so that the switch in hydraulic power will lag the switch in vacuum to assure that the vacuum hold has been removed from the center table 14 and placed on the end tables 12, 13 before the center table 14 starts back on its return travel.

Drying and return travel phase The sheet having been advanced an amount equal to the repeat print length plus the over-advance distance is ready to be dried since the last repeat print is under the drying hood 37. Concurrently with the drying, the power cylinder 42 is retracted by hydraulic pressure in its left chamber 43L. Thus both return travel and drying occur concurrently. The retraction of the cylinder 42 opens the advance contact block switch 62s. However, this brings about no change in the control relay set up just described since a holding circuit through return completed relay 88 contact 88a maintains the advance completed relay 92 energized throughout the return travel.

During the return travel of the center table 14 as well as during the advance travel of the table 14, the printing screens 34 are in the halfway up position, out of contact with the material to be printed, held in such position by the lift-oflf piston 82. Because the lift-off control relay remains unenergized throughout both advance and return travel, the ports in the lift off valve 83 supply hydraulic pressure to piston 82 in a direction tending to lower the screens 34. However, the screens are not lowered the full distance because the escape of oil from the end 96 of the cylinder within which the piston 82 moves is blocked by the lower rest solenoid 97 which solenoid will not open the valve at the piston end 96 unless that solenoid 97 is energized.

The return travel is stopped by the over-advance contact block 99 which block is located in front of the return contact block by a distance equal to the over-advance distance, which in the embodiment shown is approximately eight inches. To minimize shock, damage and noise, a return throttling control piston 98 causes a gradual deceleration of the power cylinder 42 as the cylinder 42 approaches the over-advance contact block 99.

At over-advance contact phase The position of the over-advance contact block 99 is determined by the over-advance control relay 100. When the over-advance control relay 100 is energized, contact 1000 supplies positive voltage to terminal 102a of the over-advance solenoid 102 which causes the ports in the over-advance hydraulic valve 103 to line up so as to supply fluid under pressure to the right side, as seen in FIG. 2, of the over-advance piston 104, thus retracting the over-advance contact block 99. When the control relay 100 is unenergized, positive voltage is supplied to terminal 102b through contact 100b and thus switching the hydraulic ports causing the piston 104 to advance the over-advance contact block 99. When in an advanced position, the over-advance contact block 99 extends past the return contact block 87 by an amount equal to the over-advance distance; see FIG. 4.

During the return travel phase, the over-advance control relay 100 is unenergized, and thus the power cylinder 42 abuts into and is stopped by the over-advance contact block 99 after having retracted from the advance contact block 62 by an amount equal to the repeat print width. Contact with block 99 closes over-advance switch 99s which energizes vacuum reverser relay 94. The energization of relay 94 switches the positive voltage, fed through advance complete relay contact 920, from vacuum reverser relay contact 94c to contact 94b and thus switches the vacuum reverser solenoid so that vacuum is returned to the center movable table 14. A holding circuit through return completed relay contact 88b and vacuum reverser relay contact 94a will hold relay 94 energized as long as the return completed relay 88 remains unenergized.

The energization of relay 94 also energizes the overadvance control relay through the circuit established by the closed contact 94] and the contact 88b. After a half-second time delay which is built into the relay 100, contact 1001) opens, contact 100c closes and thereby the solenoid 102 is switched so that the over-advance piston 104 is retracted. The over-advance contact block 99 thus retracts and ceases to hold the power cylinder 42 against completing its return trip. The purpose of the half-second time delay is to assure that the vacuum switches from the outside tables 12, 13 to the inside table 14 before the over-advance block 99 retracts and thus before the power cylinder 42 starts to move again.

Over-advance return travel phase With the over-advance contact block 99 retracted, the power cylinder 42 can continue its travel back to the return contact block 87. Because the closing of switch 99s caused the vacuum to be put on the center table 14, the material will be retracted as the power cylinder 42 completes this return travel through a distance equal to the over-advance distance. It is true that switch 99s will open upon the retracting of the over-advance block 99. However, that will not effect the vacuum switch made when the power cylinder 42 was stopped by the over-advance block 99 because a holding circuit through contact 94a and 88b will maintain the vacuum reverser relay 94 energized. For the reasons explained in a description of the over-advance contact phase, an energized relay 94 will keep the over-advance block 99 retracted and will leave vacuum on the movable center table 14.

Return completed phase Switch 87s and micro-switch 105, both on the return contact block 87, are both closed by the power cylinder 42 as the cylinder 42 comes to rest against the block 87, as shown in FIG. 5.

The most immediately significant operational change made by the closing of micro-switch 105 is the supplying of DC. to energize the lower rest solenoid 97 through contact 80d. Energizing solenoid 97 opens the valve at the cylinder end 96 and thus permits the lift-01f piston 82 to complete the lowering of the screens 34 onto the print table 12, 13, 14. The lowering of the piston 82 closes liftolf down micro-switch 84 which energizes primary squeegee control relay 76 through contact 740. The resulting closing of contact 76b sends a signal to the printing control relays 111, 114 to start the printing phase.

However, before describing the printing phase, the consequence of the concurrent closing of switch 87s with switch 105 must be understood, since the closing of switch 87s brings about a number of changes which are preparatory to the next or printing phase.

The closing of switch 87s energizes return completed relay 88 which opens contact 88a thereby de-energizing advance completed relay 92. The consequent closing of contact 92b completes a holding circuit to the overadvance control relay 100. The opening of contact 88b de-energizes the vacuum reverser relay 94. The consequent opening of contact 94] does not aifect the overadvance control relay 100 since that relay is held energized by the holding circuit just mentioned through contacts 100a and 92b.

The de-energization of relay 92 also does not affect the vacuum reverser solenoid 90 since the switch in vacuum reverser relay 94 is accompanied by a switch of positive voltage from contact 920 to contact 880, thus keeping positive voltage supplied to terminal 90a of the solenoid 90 and so keeping vacuum on the center table 14. Before switch 87s was closed positive voltage was put on terminal 90a through contacts 92c and 94b. On the closing of switch 87s, positive voltage is maintained on terminal 90a but now through contacts 880 and 94a.

The de-energization of relay 92 and consequent opening of contact 92d also does not affect advance-return control relay 59 since that relay stays energized by liftoff up micro-switch 106 through a holding circuit comprised of contact 590.

Printing phase The printing phase will not be described in as great detail as the other phases since it involves elements and arrangements known to the art and is tied in to the rest of the controls solely through the primary squeegee control relay 76. When the primary control relay 76 is energized, contact 76b closes to energize the advance squeegee power relay 111 through switch 112 and contact 78a. The energization of power relay 111 closes contact 111d and thus energizes the return secondary control relay 77. The power relay 111 when energized closes contacts 111a, 111b, 1110 to drive the squeegees forward one stroke. The sequence of events after this point depends on the setting of the stroke selector switch 110. Depending on the setting of the switch 110, the secondary squeegee control relays 77 and 78 will cause the squeegee power relays 111 and 114 to drive the squeegees either one stroke forward or one forward and one return stroke during each cycle.

In either case, when the squeegees complete the printing operation both secondary squeegee control relays 77 and 78 will be energized, at which point what has been arbitrarily called the printing completed phase will start.

Printing completed phase The printing completed phase started this cyclic description. There is no need to restate all that was stated there and only enough will now be stataed to indicate the cyclic continuity.

When both of the secondary control relays 77 and 78 have become energized, contacts 77d and 78e will be closed thereby energizing lift-off control relay through contacts 5b, 77d and 78e. An energized control relay 80 switches the lift-off solenoid 81 to send the piston 82 up. As the piston 82 goes up, lifting the screens 34, the piston strikes the lift-off down micro-switch 84 thereby opening that micro-switch 84 and de-energizing the primary squeegee control relay 76. As a consequence of the deenergization of the primary squeegee control relay 76 all relays '77, 78, 111, 114 driving or controlling the squeegees become de-energized and are ready to run through the printing phase on the next cycle.

If the stop button 72 were to be pushed during the printing the squeegees would complete their printing operation and because stop-go relay 74 would have been deenergized, no signal would be transmitted to the lift-off control relay 80. Thus the operation would stop short of the energization of relay 80 or the de-energization of relay 76 or the other squeegee control relays 77 and 78. Thereafter the pressing of the Go button 73 by energizing relay 74 would start the cycle exactly as described under the first printing completed phase discussed above.

However, under this cyclic description, assuming that the cycles are continuously run through, the piston 82, which has just opened micro-switch 84 to de-energize all squeegee control relays, continues upwards until it opens lift-oil up micro-switch 106. The opening of microswitch 106 de-energizes advance control relay 59 so that the advance return solenoid 58 switches and puts hydraulic pressure on the power cylinder 42 to move that cylinder 42 through an advance travel phase.

The just mentioned travel of the lift-off piston upwards to switch 106 occurs because the lift-off control relay 80 remains energized even after the opening of switches 77d and 78e since a holding circuit through contacts 800 and advance-return control relay contact 59d supplies excitation to the relay 80. However, as just indicated, the opening of switch 106 de-energizes relay 59 and thereby opens contact 59d so that the relay 80 becomes de-energized just after the piston 82 has completed its travel up to switch 106. The de-energization of relay 80 switches the lift-oil solenoid 81 and brings the piston 82 down.

However, the piston 82 will not settle all the way down but will hold the screens 34 in a half way position. There is a time delay of 0.5 second in the advance-return solenoid 58 so that the above changes can take place before the power cylinder 4-2 advances. However, the lowering of the piston 82 is slow enough so that the cylinder 42 has started on the advance travel phase by the time the piston 82 has descended to the half way down position. Therefore switch has been opened as the cylinder 42 leaves the contact block 87 and the lower rest solenoid becomes de-energized to block the valve at the piston end 96. This prevents the piston 82 and the associated screens 34 from dropping all the way down. The screens remain in this half way down position until the switch 105 is again closed on the return completed phase.

Although an embodiment of the invention has been described with considerable particularity, it must be remembered that one skilled in the art will readily see many modifications which may be made in the described embodiment without going outside of the true scope of the invention. The invention resides in the technique of incorporating an overadvance segment in the advance travel so that the last repeat print can be completely dried and then having a means for bringing back the material by the amount of the overadvance so that the next repeat print may be made and a continuous design printed. It is this which is new to the art and which makes possible the rapid printing of repeat prints in a continuous pattern.

Accordingly, the movable table which in the embodiment is hydraulically powered could be powered by any means. The vacuum grip preferred to hold and move the material to be printed could be any type of grip that would suit the purpose. Certainly an electrical relay control means is the most practical for this application but use of other control means such as electronic flip-flop circuits would achieve the same purpose yet be within the scope of the invention.

It is intended therefore in the appended claims to include all such modifications as fall within the true scope of the invention.

What we claim is:

1. A silk screen printing machine for printing on material comprising a print table having a stationary and a movable portion, vacuum means associated with said table to provide a vacuum to hold said material to said table, power means operatively coupled to said movable portion of said table to impart a linear excursion to said movable portion, return switching means at the beginning of said excursion to provide a return control signal, ad vance switching means at the end of said excursion to provide an advance control signal, power reverser means operatively coupled to said power means and responsive to said return control signal and to said advance control signal to switch the direction of motion of said movable portion of said table, overadvance switching means at a point intermediate between the beginning and end of said excursion to provide an overadvance control signal on the return portion of said linear excursion and vacuum reverser means operatively coupled to said vacuum holding means responsive to said advance control signal to switch said vacuum from said movable portion to said stationary portion of said table and responsive to said overadvance control signal to switch said vacuum from said stationary portion to said movable portion of said table.

2. The machine of claim 1 including a delay means to assure that said response of said vacuum reverser means to said advance control signal precedes the response of said power reverser means to said advance control signal.

3. The machine of claim 1 including a means for halting said movable portion of said table at said intermediate point during the return portion of said linear excursion for a period of time adequate to permit the switching of said vacuum by said vacuum reverser means in response to said overadvance control signal from said stationary portion to said movable portion of said table.

4. A machine for printing successive repeat prints on sheet material comprising a print table on which said sheet material lies when being printed, holding means associated with said table to hold said material to said table, a movable portion of said table, power means coupled to said movable portion of said table to impart linear motion to said movable portion, said linear motion being limited to an excursion equal to the length of one of said repeat prints plus an overadvance, return switching means at the beginning of said excursion to provide a return control signal, overadvance switching means at the overadvance distance after the beginning of said excursion to provide an overadvance control signal, advance switching means at the end of said excursion to provide an advance control signal, power reverser means coupled to said power means and responsive to said return control signal and to said advance control signal to switch the direction of motion of said movable portion of said table, and holding reverser means coupled to said holding means and responsive to said advance control signal and to said overadvance control signal to switch said holding means off and on to said movable portion of said table.

5. A machine for printing successive repeat prints on sheet material comprising a print table on which said sheet material lies when being printed, holding means associated with said table to hold said material to said table, a movable portion of said table, power means coupled to said movable portion to impart linear oscillatory motion to said movable portion, said linear motion being limited to an excursion equal to the length of one of said repeat prints plus an overadvance, return switching means operatively coupled to said movable portion to provide a return control signal when said movable portion is at the beginning of said excursion, advance switching means operatively coupled to said movable portion to provide an advance control signal when said movable portion is at the end of said excursion, overadvance control means operatively coupled to said movable portion to provide an overadvance control signal when said movable portion is returning to the beginning of said excursion and is at a distance from said beginning equal to said overadvance, printing means responsive to said return control signal to print one of said repeat prints on said material when said movable portion returns to said beginning of said excursion and to provide a printing completed control signal at the completion of the print of one of said repeat prints, power reverser means coupled to said power means and responsive to said advance control signal and to said printing completed control signal to switch the direction of travel of said movable portion upon receipt of said signal, and holding reverser means coupled to said holding means and responsive to said overadvance control signal to hold said material to said movable portion upon receipt of said overadvance control signal and responsive to said advance control signal to remove the hold on said material by said movable portion upon receipt of said advance control signal.

References Cited by the Examiner UNITED STATES PATENTS 1,472,466 10/1923 Gammeter 226-143 2,039,236 4/1936 Meisel 226-143 X 2,267,596 12/1941 Montague et al 101-123 2,375,237 5/1945 Morgan et al. 101-114 2,419,694 4/1947 Shuttleworth et al. 101-129 2,421,410 6/1947 Bucklin 101-129 2,612,835 10/1952 Marek et al. 101-126 2,710,577 6/1955 Prett 101-126 X 2,923,235 2/ 1960 Voegelin 101-407 FOREIGN PATENTS 813,307 2/1937 France.

578,936 6/ 1933 Germany.

738,349 10/1955 Great Britain.

ROBERT E. PULFREY, Primary Examiner.

DAVID KLEIN, Examiner.

HARLEIGH P. EWELL, Assistant Examiner. 

1. A SILK SCREEN PRINTING MACHINE FOR PRINTING ON MATERIAL COMPRISING A PRINT TABLE HAVING A STATIONARY AND A MOVABLE PORTION, VACUUM MEANS ASSOCIATED WITH SAID TABLE TO PROVIDE A VACUUM TO HOLD SAID MATERIAL TO SAID TABLE, POWER MEANS OPERATIVELY COUPLED TO SAID MOVABLE PORTION OF SAID TABLE TO IMPART A LINEAR EXCURSION TO SAID MOVABLE PORTION, RETURN SWITCHING MEANS AT THE BEGINNING OF SAID EXCURSION TO PROVIDE A RETURN CONTROL SIGNAL, ADVANCE SWITCHING MEANS AT THE END OF SAID EXCURSION TO PROVIDE AN ADVANCE CONTROL SIGNAL, POWER REVERSER MEANS OPERATIVELY COUPLED TO SAID POWER MEANS AND RESPONSIVE TO SAID RETURN CONTROL SIGNAL AND TO ADVANCE CONTROL SIGNAL TO SWITCH THE DIRECTION OF MOTION OF SAID MOVABLE PORTION OF SAID TABLE, OVERADVANCE SWITCHING MEANS AT A POINT INTERMEDIATE BETWEEN THE BEGINNING AND END OF SAID EXCURSION TO PROVIDE AN OVERADVANCE CONTROL SIGNAL ON THE RETURN PORTION OF SAID LINEAR EXCURSION AND VACUUM REVERSER MEANS OPERATIVELY COUPLED TO SAID VACUUM HOLDING MEANS RESPONSIVE TO SAID ADVANCE CONTROL SIGNAL TO SWITCH SAID VACUUM FROM SAID MOVABLE PORTION OF SAID STATIONARY PORTION OF SAID TABLE AND RESPONSIVE TO SAID OVERADVANCE CONTROL SIGNAL TO SWITCH SAID VACUUM FROM SAID STATIONARY PORTION OF SAID MOVABLE PORTION OF SAID TABLE. 